The present application relates to a polymeric material for artificial bones. More specifically, the present application relates to a novel polymeric material for artificial bones which can effectively form an apatite layer similar to that of bones in a simulated body fluid.
It has been known that the bone is a composite with a thee-dimensional structure formed exquisitely from fine crystals of apatite, an inorganic substance, deposited on fibers of collagen, an organic substance. Various approaches have been studied thus far for finding a method to artificially build a similar structure.
However, all such methods employ aqueous solutions with very high concentrations of ions, as compared with the ion concentrations of body fluid, for forming an apatite layer. Such aqueous solutions can only form apatite layers differing greatly in structure and composition from those of bones in a living body, and the materials obtained therefrom cannot be readily joined with living bones.
Under these circumstances, we, the inventors of the present invention, have discovered the usefulness of a method imitating in vivo reactions (a biomimetic method), and have devoted ourselves to the search for a method to deposit apatite on an organic polymer base. However, we had not been able to find any polymeric material thus far that could be used to effectively deposit a large amount of apatite with structure and tissue close to those of the inorganic substance in bones.
For example, we experimented with the use of cellulose base as the organic polymer, taking in consideration its hydrophilic property and the reactivity of the OH group, and tried to form an apatite layer in a simulated body fluid by introducing onto the surface of the base a silanol (Sixe2x80x94OH) group known for being effective in the nucleation of apatite. However, we have found that the apatite layer formation was too slow for this method to be effective.
The object of the present invention is, therefore, to overcome the above problems and to provide a novel polymeric material for artificial bones, which can more effectively form an apatite layer in a simulated body fluid, with structure and composition showing mechanical properties similar to those of bones.
To attain the above object, provided as the first embodiment is a polymeric material for artificial bones, comprising a solid or gel-form base containing, as its main component, a polysaccharide containing carboxyl groups or their derivatives, or a polysaccharide having carboxyl groups or their derivatives introduced to it, and has calcium ions bonded thereto.
Provided as the second embodiment is a polymeric material for artificial bones, in which the solid base is in the form of a porous solid, fiber, film, or bulk. Provided as the third embodiment is a polymeric material for artificial bones in which the polysaccharide is a natural polysaccharide containing carboxyl groups, or a polysaccharide derivative having carboxyl groups introduced to it.
Also, as the fourth embodiment, a polymeric material for artificial bones, on which an apatite layer can form in a simulated body fluid, is provided, and as the fifth embodiment, a method of manufacturing a polymeric material for artificial bones of the above embodiments comprising the contact of a solid or gel-form base containing, as its main component, a polysaccharide containing carboxyl groups or their derivatives, or a polysaccharide having carboxyl groups or their derivatives introduced into it, with a solution containing calcium ions, to crosslink the said carboxyl groups or their derivatives. Furthermore, as the sixth embodiment, an artificial bone structure comprising a polymeric material for artificial bones as above, with an apatite layer formed on its surface, is provided.